The severe flood warnings are for Cornwall and north Devon coasts and the river Severn, south of Gloucester.

Lesser warnings remain in place for many parts of Britain, including the already-flooded Somerset Levels and west Wales, where 49 flood warnings and 15 alerts were issued on Saturday morning.

The Thames flood barriers will be raised on Saturday to reduce flooding along the Thames and the government's emergency Cobra committee is expected to meet.

Kate Marks, the Environment Agency's flood risk manager, said: "A low pressure system combining with high tides brings a risk of coastal flooding to many parts of England. The risk is highest for south-west England, although many coastal areas will be affected and the public should stay away from coastlines and tidal areas and not drive through floodwater."

She warned that gales and waves could lead to the breaching of flood defences and sea walls, property flooding and travel disruption.

Personnel from all three branches of the armed forces are currently on standby to help villages in Somerset cut off by the floods.

There has been growing discontent in the county, where criticism has been levied at the government and environment officials for not doing enough.

"Like everybody across the country I feel enormous sympathy for the people who live on the Somerset Levels and are suffering from the devastating impact of the flooding," he wrote.

"I know that a great deal of work has been done to try and alleviate the situation but it is not acceptable for people to have to live like this almost four weeks later – and I am not ruling out any option to get this problem sorted out.

"The government is doing everything we can to help people recover as quickly as possible where they have suffered damage to their homes and businesses. Dredging will begin as soon it is safe to do so – and the Environment Agency will spend the coming months improving river flows across the south-west, including dredging and weed clearance."